/*
 * (C) Copyright 2014-2016, by Dimitrios Michail
 *
 * JHeaps Library
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jheaps.tree

import org.jheaps.AddressableHeap
import org.jheaps.AddressableHeapFactory
import org.jheaps.MergeableAddressableHeap

/**
 * Reflected double ended heaps based on pairing heaps. The heap is sorted
 * according to the [natural ordering][Comparable] of its keys, or by
 * a [Comparator] provided at heap creation time, depending on which
 * constructor is used.
 *
 *
 *
 * This class implements a general technique which uses two [PairingHeap]s
 * to implement a double ended heap, described in detail in the following
 * [paper](http://dx.doi.org/10.1016/S0020-0190(02)00501-X):
 *
 *  * C. Makris, A. Tsakalidis, and K. Tsichlas. Reflected min-max heaps.
 * Information Processing Letters, 86(4), 209--214, 2003.
 *
 *
 *
 *
 * This implementation provides amortized O(log(n)) time cost for the
 * `insert`, `deleteMin`, `deleteMax`, `decreaseKey`,
 * `increaseKey`, and `delete` operations. `findMin` and
 * `findMax` are worst-case O(1) operations. The operation `meld` is
 * amortized O(log(n)).
 *
 *
 *
 * All the above bounds, however, assume that the user does not perform
 * cascading melds on heaps such as:
 *
 * <pre>
 * d.meld(e);
 * c.meld(d);
 * b.meld(c);
 * a.meld(b);
</pre> *
 *
 * The above scenario, although efficiently supported by using union-find with
 * path compression, invalidates the claimed bounds.
 *
 *
 *
 * Note that the ordering maintained by a this heap, like any heap, and whether
 * or not an explicit comparator is provided, must be *consistent with
 * `equals`* if this heap is to correctly implement the
 * `AddressableHeap` interface. (See `Comparable` or
 * `Comparator` for a precise definition of *consistent with
 * equals*.) This is so because the `AddressableHeap` interface is
 * defined in terms of the `equals` operation, but this heap performs all
 * key comparisons using its `compareTo` (or `compare`) method, so
 * two keys that are deemed equal by this method are, from the standpoint of
 * this heap, equal. The behavior of a heap *is* well-defined even if its
 * ordering is inconsistent with `equals`; it just fails to obey the
 * general contract of the `AddressableHeap` interface.
 *
 *
 *
 * **Note that this implementation is not synchronized.** If
 * multiple threads access a heap concurrently, and at least one of the threads
 * modifies the heap structurally, it *must* be synchronized externally.
 * (A structural modification is any operation that adds or deletes one or more
 * elements or changing the key of some element.) This is typically accomplished
 * by synchronizing on some object that naturally encapsulates the heap.
 *
 * @param <K>
 * the type of keys maintained by this heap
 * @param <V>
 * the type of values maintained by this heap
 *
 * @author Dimitrios Michail
</V></K> */
class ReflectedPairingHeap<K, V>
@JvmOverloads constructor(comparator: Comparator<in K?>? = null) : ReflectedHeap<K, V>(Factory(), comparator) {
    private class Factory<K, V> : AddressableHeapFactory<K, HandleMap<K,V>, MergeableAddressableHeap<K, HandleMap<K, V>>> {
        override fun get(comparator: Comparator<in K?>?): MergeableAddressableHeap<K, HandleMap<K, V>> {
            return PairingHeap(comparator)
        }
    }
}
